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Monthly Archives: March 2014

The same scene, good “old” tomatoes…

These photos were taken at the same time as the previous exercise using the same lens and equipment, this time I’ve focused using the middle point and I’ve set the aperture to the widest, the middle and the smallest setting. Changing the aperture is one way to control depth of field. Depth of field or DOF is referring to the sharp area on a photo, in front of and behind the focus point.

30 mm, f/1.4, 1/60, ISO 100

30 mm, f/1.4, 1/60, ISO 100

30 mm, f/8.0, 0.5 sec, ISO 100

30 mm, f/8.0, 0.5 sec, ISO 100

 

30 mm, f/16, 2.0 sec, ISO 100

30 mm, f/16, 2.0 sec, ISO 100

The wide aperture of f/1.4 creates very shallow depth of field, only 4 tomatoes in focus and standing apart from the others but still not as sharp as on the other pictures. The aperture of f/8.0 gives a pleasing image, the middle part is definitely sharper, noticeably larger depth of field slowly fading away towards the edges of the picture giving a smooth, natural effect; the last one with f/16 results the largest depth of field, it’s sharp and shows every detail.

In terms of sharpness I prefer the second image, however I could have done it with a larger aperture to achieve better sharpness, 2.5 to 3 stops down from the lens’s maximum aperture also known as the lens’ “sweet spot”. Using my 30 mm f/1.4 lens this value is somewhere between f/2.8 and f/4 which would also create a shallower depth of field.

In terms of focus I could have done better choosing a bit wider aperture than f/16 knowing that is my lens’ minimum aperture, following the same theory with the maximum aperture, avoid using the lens on its limits the achieve better results.

I also noticed I haven’t paid to much attention to shutter speed – as I shot this in aperture priority – It stopped down to 2 seconds in the end, which would have caused problems if I would have shot without tripod. Nevertheless I should have adjusted the ISO accordingly to reduce the risk of blurry images.

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Find a scene which has depth…

The main reason I wanted to get a DSLR camera is that all of my pictures had large depth of field so everything was sharp, it was no difference between the subject and the background which is most of the time quite distracting compare to pictures with clear subject and out of focus background. I reckon it is more appealing to the human eye when subjects are really stand out.

I went for a walk thinking I can find my subject outside but the rain has cancelled my plans quickly so I decided to create something with these photogenic tomatoes. For this exercise I used my Canon 60D with Sigma 30 mm f /1.4 DC Art lens, a tripod, a white paper board to get a perfect background and I positioned to the window to get as much natural light as possible. I always shoot in RAW to capture all image data recorded by the sensor which will allow me to get better quality pictures as well as correct problems when it comes to post-processing. Having said that I have adjusted the exposure and I have enabled lens correction in order to get rid of the minimal amount of vignetting.

I took all three photos with same settings, the largest aperture to isolate the tomatoes even more, obviously the only thing I changed is the focus point, on the first picture I focused on the bottom (first tomato), on the second image the focus point set in the middle of the frame, on the third one I chose the top focus point.

30 mm, f /1.4, 1/80, ISO 100

30 mm, f /1.4, 1/80, ISO 100

30 mm, f /1.4, 1/80, ISO 100

30 mm, f /1.4, 1/80, ISO 100

30 mm, f /1.4, 1/80, ISO 100

30 mm, f /1.4, 1/80, ISO 100

The smaller the number the larger the aperture, large aperture means shallow depth of field resulting blurry background.

I prefer the first and the second image simply because I like to look at these pictures, the third one becomes uncomfortable to my eyes because of the large blurry foreground.

The first image is all about the single tomato on the front, I reckon this type of focus would work well in product photography as it has a strong feel of the product, in this case, the tomato. The second one is softer, more effortless, it looks like they’ve been sitting on the kitchen worktop waiting to be made into a delicious Italian dish.

Taking the first steps with OCA includes numerous exercises. These are great help to get to know the camera better, understanding focal length, angle of view, focusing on still and moving subjects with different speed and aperture.

Focal length is the distance between the lens and the sensor when the lens focused at infinity measured in mm, the angle of view is the amount of a scene that a lens can take in measured in degrees. A 50 mm lens is considered to be a standard lens for a 35 mm film camera as it produces an image that through the human eye would be recognized as normal and not distorted in any way. According to the manual my Canon 60D camera has a smaller sensor of  22.3 x 14.9 mm, compared to full frame size of  36 x 24 mm which means my Sigma 30 mm 1.4  Art lens becomes 48 mm as a result of 1.6 crop factor.

To calculate the ‘actual’ effective angle of view I use Pythagoras’ Theorem to determine the longest side (i.e. the diagonal length or hypotenuse) of a right-angled triangle. Pythagoras’ Theorem states that in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides. A^2 + B^2 = C^2, where “C” is equal to the length of the hypotenuse and “a” and “b” are the lengths of the other two sides. (22.3 x 22.3)  + (14.9 x 14.9) = C^2 497.29 + 222.01 = C^2 719.3 = C^2 C = 26.82 mm is the length of the diagonal of the 60D sensor. Therefore the diagonal measurement of the full frame sensor is 43.3 mm compare to the cropped sensor’s 26.82 mm 43.3 / 26.82 = 1.61 actual crop factor.

For this exercise I used my Canon 60D with 15-85 mm f/3.5-5.6 IS USM lens and a tripod, I shot in Raw from the bridge over River Wharfe in Ilkley, West Yorkshire and processed the images in Lightroom.

15 mm, f/ 3.5, 1/1000, ISO 200

15 mm, f/ 3.5, 1/1000, ISO 200

29 mm, f/ 4.5, 1/400, ISO 200

29 mm, f/ 4.5, 1/400, ISO 200

85 mm, f/ 5.6, 1/320, ISO 200

85 mm, f/ 5.6, 1/320, ISO 200

I took the exposure information from Lightroom’s metadata panel. I printed these images onto A4 paper with my Canon IP4600 photo printer, I noticed that the colours are different on the screen, I made some adjustments but it didn’t work, I have to calibrate properly.

I went back to the same spot, the top of the bridge and I noticed that if I hold the second picture approx 0.5 m away from me it will appear the closest to my eye, 29 mm x 1.6 crop factor resulting 46.6 mm,  however I could have done better because it was still slightly further than what I have actually seen from there. Looking at my first picture taken at 15 mm wasn’t too comfortable, I hold that approx 25 cm away from my eyes. I could not hold the third one as far as I needed to because of the limitation of the space but studying the first and the second picture helped me to understand how focal length works with different size of sensors and how it appears to the human eye. I also realized I haven’t paid attention to aperture, I should have shot with few stops smaller (larger number) to get a sharper image.